Perhaps you might chance upon the dictionary at some old bookstall.

或许你会在旧书摊上偶然发现这本字典。

youdao

However it is non official and will be known to people who chance upon it (for now).

然而，它(blog)不是官方的而且将会被碰巧遇到它的人所熟知(对现在来说)。

youdao

It happened one day that the son of a king, while riding in the forest, came by chance upon the dwarfs' house and asked for a night's lodging.

有天有件事情发生了，一个国王的儿子，当他骑马来到这个森林，偶尔来到矮人们的房子晚上要求投宿。

youdao

It's not every day you chance upon a Sri Lankan British singer with a Kingston-meets-cockney brogue, rapping about revolution.

NPR: M.I.A.: Rapper and Daughter of Revolution

Then I chance upon DiscVault .

CNN: WINDOWS SHOPPING

It was, accordingly, declared Germany's first victim, a chance pounced upon by Austria's post-war politicians (many of whom were themselves victims of Nazism).

ECONOMIST: Austria since Hitler